Limb salvage after successful pedal bypass grafting is associated with improved long-term survival.

OBJECTIVES: Assessments of outcome after reconstruction for critical limb ischemia frequently ignore functional result and long-term morbidity and mortality. This study was undertaken to identify factors affecting long-term clinical outcome and survival after pedal bypass grafting. METHODS: The clinical data of 256 consecutive patients who underwent pedal bypass grafting for critical limb ischemia over a 12-year period were retrospectively analyzed. RESULTS: A total of 174 men and 82 women (median age, 70 years; range, 30-91 years) underwent 280 pedal bypass graft placements with autologous vein. Seventy-five percent of the patients were diabetic, and 20% had renal insufficiency (serum creatinine level > 2 mg/dL). The in-hospital mortality rate was 1.6% (4/256). The mean follow-up was 2.7 years (range, 0.1-10.1 years). Rates of primary and secondary patency, limb salvage, and survival at 5 years were 58%, 71%, 78%, 60%, respectively. A total of 160 limbs (57%) required additional interventions. Nineteen early graft thrombectomies/revisions and nine early amputations were performed. One hundred thirty-eight late interventions included 31 graft salvage procedures, 27 wound debridements, and 34 minor and 42 major amputations. At last follow-up or death, 219 (78%) limbs were being used for ambulation. End-stage renal disease (ESRD) and composite vein grafts predicted limb loss (P <.001, P <.001, respectively). Overall survival at 5 years was 60%. Survival after amputation was 79%, 53%, and 26% at 1, 3, and 5 years. Amputation and ESRD predicted higher mortality (P =.014, P =.0001, respectively). CONCLUSIONS: Pedal bypass grafting resulted in good functional limb salvage, but at the expense of multiple interventions in more than half the cases. ESRD and composite vein graft were associated with poor long-term limb salvage. Amputation after bypass grafting was associated with significantly worse long-term survival.

Pedal bypass for limb salvage: impact of diabetes on long-term outcome.

Use of pedal bypass can salvage limbs of patients with critical ischemia. The aim of this study was to evaluate the results of surgical revascularization of pedal arteries in diabetic patients and to assess the impact of diabetes on long-term outcome. We performed a retrospective analysis of all consecutive pedal bypasses done between January 1, 1987 and December 31, 1997. Demographic data, surgical indications, operative variables, and postoperative results including graft patency and limb salvage were compared between diabetic and nondiabetic patients. The results of this comparison showed that pedal bypass can safely and effectively relieve critical ischemia in diabetic patients. Diabetics have less early graft thrombosis and superior long-term graft patency. Despite higher incidence of renal insufficiency or failure and more tissue loss, diabetics can achieve similar excellent limb salvage rates. This outcome justifies aggressive revascularization of pedal arteries in diabetic as well as nondiabetic patients with critical limb ischemia.

Replacement of the inferior vena cava for malignancy: an update.

OBJECTIVES: Resection and replacement of the inferior vena cava (IVC) to remove malignant disease is a formidable procedure. Since our initial report with IVC replacement for malignancy, we have maintained an aggressive approach to these patients. The purpose of this review is to update our experience with regard to patient selection, operative technique, and early and late outcome. METHODS: All patients who had IVC replacement for primary (n = 2) or secondary (n = 27) vena cava tumors from April 1990 to May 1999 were reviewed. Tumor location and type, clinical presentation, the segment of IVC replaced, graft patency, performance status of the patient, and tumor recurrence and survival data were collected. Late follow-up data were available for all but one patient. The IVC was replaced in 28 patients with large diameter (> or =14 mm) externally supported ePTFE grafts and with a panel graft of superficial femoral vein in the other. Three patients had a femoral arteriovenous fistula. Graft patency was determined before hospital dismissal and in follow-up by vena cavography, computed tomography, ultrasonography, or magnetic resonance imaging. RESULTS: There were 18 women and 11 men, with a mean age of 53.1 years (range, 16-88 years). Over one half of patients had symptoms from their tumor. IVC replacement was at the suprarenal segment in 15 patients, of whom 13 had concomitant major hepatic resection, at the infrarenal segment in 10, at both caval segments in three, and at the renal vein confluence in one. There were two early deaths (6.9%). One patient died intraoperatively of coagulopathy during liver resection and suprarenal IVC replacement. The other death occurred 4 months postoperatively, from multisystem organ failure that resulted in graft infection and occlusion. Twelve patients had one or more major complications- cardiopulmonary problems in five; bleeding in five; chylous ascites or large pleural effusions in two patients each; and lower extremity edema with tibial vein thrombosis in one. The mean follow-up was 2.8 years (range, 2.7 months to 6.3 years). Two late graft occlusions occurred: one at 7.5 months, the other, from tumor recurrence, at 6.3 years. There have been no other late graft-related complications. All 11 late deaths were caused by the progression of malignant disease. Of 16 survivors, 12 have no evidence of disease and four have either regional or distant metastatic recurrence. Initial postoperative performance status was good or excellent for most survivors. CONCLUSIONS: Aggressive surgical management may offer the only chance for cure or palliation of symptoms for patients with primary or secondary IVC tumors. Our experience suggests that vena cava replacement may be performed safely with low graft-related morbidity and good patency in carefully selected patients.

The benefits of secondary interventions in patients with failing or failed pedal bypass grafts.

BACKGROUND: Autogenous bypass grafts to pedal arteries have successfully salvaged limbs and restored function in patients with critical ischemia. The benefits of secondary interventions to save failing or already failed grafts remains uncertain. METHODS: A retrospective analysis was made of consecutive pedal bypasses performed between 1987 and 1998. Patency and limb salvage by life-table analysis and variables affecting outcome were compared with the log-rank test. RESULTS: Two hundred thirteen patients, 144 males, 69 females (mean age 68 years, range 30 to 91) underwent pedal bypass grafting in 228 limbs using autogenous vein grafts (nonreversed saphenous vein, n = 190; reversed, n = 15; composite, n = 23). One-hundred fifty-seven patients were diabetic, 34 had renal insufficiency (serum creatinine >2.0), and 14 were on dialysis. Gangrene or ulceration were present in 224 patients, rest pain in 24. Cumulative primary and secondary patency rates were 57% and 67% at 5 years. Limb salvage was 78% at 5 years. Secondary interventions in 46 patients included patch angioplasty/surgical revision (n = 28), thrombectomy (n = 15), thrombolysis (n = 11), and balloon angioplasty (n = 6). Patency in 19 of 26 (73%) failed grafts and in 19 of 20 (95%) failing grafts could be restored initially. Cumulative 2-year patency and limb salvage rates following reinterventions were 36% and 58%, respectively. Patency rates and limb salvage for failed grafts (7%, 44%) were significantly worse than those for failing grafts (81%, 77%; P <0.0001, P <0.05, respectively). All patients with renal insufficiency who underwent reinterventions for failed or failing grafts required major amputation within 1 year (P <0.0001 versus those without renal insufficiency). CONCLUSION: Autogenous pedal bypass grafts are durable operations with excellent long-term patency and limb salvage rates. Revision of failing grafts has been effective using both endovascular and surgical techniques. Failed grafts have poor long-term patency and moderate limb salvage rates, and our data do not justify secondary procedures to attempt to save failed grafts in patients with renal insufficiency.

Aorto-caval and ilio-iliac arteriovenous fistulae.

BACKGROUND: To determine optimal management of major abdominal arteriovenous fistulae and define factors affecting outcome. METHODS: We reviewed clinical data of 18 patients, 16 males and 2 females, who underwent repair of major abdominal arteriovenous fistulae between 1970 and 1997. RESULTS: Sixteen patients had primary fistula, caused by rupture of an atherosclerotic aortic or aortoiliac aneurysm into the inferior vena cava (IVC), iliac, or left renal vein. Two had secondary, iatrogenic arteriovenous fistulae. Seventeen patients (94%) were symptomatic, 11 (62%) had acute presentation. Fistula was diagnosed preoperatively in 8 (44%). Fistula closure (direct suture 16, patch 1, iliac vein ligation 1) was followed by aortoiliac reconstruction in all patients. Caval clip was placed in 3 patients. Early mortality was 6%; 7 patients had major complications. During follow-up (mean 6.1 years) 2 patients died of causes related to fistula closure. CONCLUSIONS: Rupture of aortoiliac aneurysms into the iliac veins or IVC carries a better prognosis than intraperitoneal, retroperitoneal, or enteric rupture. Although preoperative diagnosis is ideal, a high index of suspicion, careful repair avoiding pulmonary embolization, and blood salvage were all helpful in keeping morbidity and mortality low. Our data suggest that IVC interruption is seldom warranted.

Microscope-aided pedal bypass is an effective and low-risk operation to salvage the ischemic foot.

BACKGROUND: The aim of this study was to determine the current operative risks of the pedal bypass procedure, its durability, and the factors affecting long-term outcome. METHODS: We prospectively observed 96 patients who consecutively underwent 100 pedal bypasses using autogenous vein grafts for chronic critical ischemia. Of the 100 limbs, 91 had ischemic ulcers or gangrene, and 9 produced rest pain only. Sixty-four patients were diabetic, 21 had renal failure, and 36 had coronary artery disease. Nonreversed saphenous vein grafts were used most frequently (68 translocated, 13 in situ), followed by composite (13) and reversed vein grafts (6). Fifty-two long grafts originated from the iliac or femoral arteries, and 48 short grafts originated from the popliteal or tibial arteries. For the 100 procedures, 102 distal anastomoses were performed--68 to the dorsalis pedis, 8 to the distal posterior tibial, 10 to the common plantar, 2 to the medial plantar, 9 to the lateral plantar, 4 to the lateral tarsal, and 1 to the first dorsal metatarsal arteries--with the aid of an operating microscope. RESULTS: No patient died during the perioperative period. Two had hemodynamically insignificant myocardial infarctions. Wound complications developed in 12 patients--infection in 7 and hematoma in 5. There were 10 early graft failures, 6 of which could be salvaged, and 96 grafts were patent at dismissal. Mean follow-up was 2.1 years (range 1 month to 6.4 years). Postoperative surveillance identified 33 failed or failing grafts, 16 of which were successfully revised. At 3 years, cumulative primary and secondary patency rates were 60% and 69%, respectively. Factors correlating with increased secondary patency were intraoperative flow rate > or = 50 mL/min (P = 0.004) and diabetes (P < 0.05). Major amputations were performed on 17 limbs. The cumulative foot salvage rate at 3 years was 79%. CONCLUSION: Pedal bypass is a safe, effective, and durable procedure. It should be considered even for high-risk patients with critical limb ischemia before major amputation is contemplated.

Advanced carotid disease in patients requiring aortic reconstruction.

Perioperative stroke is a devastating complication of abdominal aortic operations. Patients requiring aortic reconstruction with advanced carotid occlusive disease pose a particularly challenging management problem regarding timing of operations. All patients (n = 121) undergoing both carotid artery endarterectomy (CEA) and abdominal aortic reconstruction (AAR) within 1 year of each other between 1979 and 1989 were reviewed. The sequence of operation was analyzed to determine its effect on early and late outcome. CEA was the first operation in 99 patients (group I); AAR was performed first in 22 patients (group II). Age, gender, number, types of risk factors, and associated medical problems were similar in both groups. Indications for CEA were: transient ischemic attacks (TIAs), recent ipsilateral stroke, or high-grade asymptomatic carotid artery stenosis exceeding 80%. Indications for aortic operation included: abdominal aortic aneurysm, aortoiliac occlusive disease, and combined aortic and renovascular disease. There were five perioperative strokes, two in group I (2%) and three in group II (14%) (p < 0.04). All strokes occurred after AAR. There were five perioperative deaths (4%), four in group I (4%) and one in group II (5%). Overall survival was significantly greater in group I compared to group II (p < 0.04); 5-year survival was 77% and 51%, respectively. Multivariate analysis demonstrated age, hypertension, and diabetes to adversely affect survival; CEA as the first procedure, however, had a protective effect. Importantly, eight strokes occurred in group I in late follow-up, but only one was ipsilateral to the CEA. We conclude that CEA in selected patients who require AAR is safe, and, when performed prior to abdominal aortic repair, reduces perioperative stroke and may improve long-term survival.

Vena cava replacement for malignant disease: is there a role?

Resection and graft replacement of the vena cava for malignant disease is rarely performed, often because of the advanced tumor stage. Since August 1987 we have selectively performed caval replacement in conjunction with tumor resection in 11 patients. Three patients had superior vena cava reconstruction (SVCR) and eight had inferior vena cava replacement (IVCR). There were six males and five females whose mean age was 59.3 years (range 24 to 75 years). Two patients, each with superior vena cava obstruction, presented with symptoms from venous compression. Malignancies involving the superior vena cava were thyroid carcinoma in two patients and lymphoma in one. Cancers requiring IVCR were leiomyosarcoma in three patients, cholangiocarcinoma in two, and malignant fibrous histiocytoma, hepatocellular carcinoma, and colon carcinoma metastatic to the liver in one each. All IVCRs and two SVCRs were performed with expanded polytetrafluoroethylene grafts. The remaining SVCR was constructed with spiral saphenous vein. Six IVCRs involved replacement of the retrohepatic inferior vena cava in conjunction with major liver resection. Mean intraoperative blood transfusions were 5.3 units (range 0 to 10 units). There were no operative deaths. Complications occurred in four patients and included postoperative bleeding in two, myocardial infarction in one, and wound infection in one. There were no perioperative graft occlusions, but one patient developed graft occlusion 2 months after SVCR. All IVCR grafts have remained patent (mean follow-up of 8.8 months). Two patients with SVCRs have died from recurrent cancer at 3.2 and 3.4 years postoperatively. Six patients with IVCRs have developed tumor recurrence either locally (n = 1), at a distant site (n = 2), or both (n = 3). Importantly, eight of nine survivors have an excellent performance status. We conclude that vena cava reconstruction for malignancy can be performed safely, has few graft-related complications, and in some patients may offer the only possibility for tumor control.

Reconstruction of large veins for nonmalignant venous occlusive disease.

To evaluate the effectiveness of venous grafting, we reviewed the management and clinical course of 28 patients (21 males and seven females) who underwent 29 reconstructions of large veins for benign disease. There were 12 patients with superior vena cava (SVC) syndrome, two with subclavian vein thrombosis, and 15 with occlusion of the inferior vena cava (IVC) or iliac veins. One of these patients underwent both IVC and SVC reconstructions. Reconstruction of the SVC was performed with spiral saphenous vein graft (SSVG) in nine patients and expanded polytetrafluoroethylene (ePTFE) in three. All seven straight SSVGs had documented patency at a median of 7 months (2 weeks to 5 years) after reconstruction. Six patients had complete relief of symptoms. Two patients with bifurcated SSVG had early occlusion of one graft limb. Two of the three ePTFE grafts needed early thrombectomy. One graft reoccluded at 6 months and two were patent at 2 and 5 years. The two subclavian vein reconstructions with axillary-jugular ePTFE grafts with an arteriovenous fistula had documented early patency. Both patients had rapid resolution of symptoms. The IVC or iliac vein was reconstructed with ePTFE graft in 11 patients, SSVG in three, and Dacron in one. A femorofemoral arteriovenous fistula was added in eight patients with ePTFE grafts. Seven of the 11 ePTFE grafts had documented patency at the last follow-up (median 9 months; range 2 weeks to 5 years). None of the three SSVGs had documented long-term patency. The one Dacron cavoatrial graft occluded at 3 years. A straight SSVG continues to be our first choice for SVC replacement. Short, large-diameter ePTFE grafts perform the best in the abdomen. Femorocaval or long iliocaval grafts need an arteriovenous fistula to maintain patency. Long-term patency after closure of the fistula is still unknown. Femorocaval grafts with poor venous inflow have limited chance of success. Failed or failing grafts may be salvaged by early thrombectomy. Venous reconstruction to treat selected patients with symptoms with large vein occlusion continues to be a viable option.

Ruptured abdominal aortic aneurysms: repair should not be denied.

The records of 231 patients (189 men, 42 women) treated during the last decade for ruptured infrarenal abdominal aortic aneurysm were reviewed to evaluate complications and mortality rates and to determine if preoperative factors would preclude attempt at surgical repair. Mean age was 73.7 years (range, 50 to 95 years). Fifty-seven patients (24.7%) were greater than or equal to 80 years of age. Sixty-eight patients (29.4%) had known abdominal aortic aneurysm before rupture. Preoperative systolic blood pressure was less than or equal to 90 mm Hg in 155 patients (67.1%). Fifty-six patients (24.2%) had cardiac arrest before operation. The overall mortality rate from admission until the end of the hospital stay was 49.4% (114 of 231). Seventeen patients (7.4%) died in the emergency department, 40 (17.3%) in the operating room, 27 (11.7%) during the first 48 postoperative hours, and 30 (13.0%) died later but during the same hospitalization. The 30-day operative mortality rate was 41.6%. Mean age of those who died was higher (75.3 years) than of those who survived (72.2 years) (p less than 0.02). Of patients greater than or equal to 80 years, 43.9% survived. Survival was lower among women (35.7%) than men (54.0%; p less than 0.04). A high APACHE II score, a low initial hematocrit, preoperative hypotension, and chronic obstructive pulmonary disease were associated multivariately with increased mortality rates (p less than 0.02). However, 59 of the 155 patients (38.1%) with preoperative hypotension survived. Deaths were high (80.4%) among patients with cardiac arrest (45 of 56); still, 28.2% of patients (11 of 39) survived repair after cardiac arrest.(ABSTRACT TRUNCATED AT 250 WORDS)

Klippel-Trenaunay syndrome: the risks and benefits of vascular interventions.

Our experience with Klippel-Trenaunay syndrome (KTS), a rare congenital malformation, has increased considerably in recent years and now includes 144 patients (65 male and 79 female patients). Hemangioma was present in 137 patients (95.1%), varicosity in 110 (76.4%), and hypertrophy of the soft tissues or bones in 134 (93.1%). In most patients (71.5%) the disease involved one lower extremity. Diagnostic workup included roentgenogram to document limb length discrepancy, noninvasive arterial and venous evaluation, contrast venography, and nuclear magnetic resonance imaging. Most patients did well without treatment or with elastic compression only. Surgical treatment for the vascular malformation in KTS is rarely needed and it continues to be controversial. To evaluate the risks and benefits of vascular interventions, we examined in detail the clinical histories of nine patients who in the last decade underwent operation for a vascular malformation of the lower extremity. In seven patients we removed varicose veins or resected hemangioma of the lower extremity. Although none was cured, all five who underwent resection of varicose veins and one of the two patients who underwent resection of a hemangioma improved. Two additional patients, however, who underwent resection of varicose veins in another institution had worsening of the symptoms. In one patient we performed deep venous reconstruction for atresia of the superficial femoral vein, using the contralateral saphenous vein. Such operation in KTS has not been reported previously. The patient has a patent graft with a competent valve and clinical improvement 6 months after the operation. Although patients with severe chronic venous insufficiency, disturbing cosmetic appearance, or complications of hemangioma may benefit from surgical treatment, detailed preoperative imaging of the extremity and pelvis with magnetic resonance imaging and contrast venography is needed to decrease complications. Rarely, reconstruction for atresia or hypoplasia of the deep veins may be needed.

Ischemic injury to the spinal cord or lumbosacral plexus after aorto-iliac reconstruction.

Between January 1, 1980, and June 30, 1989, 9 patients (6 males and 3 females) developed ischemic injury to the spinal cord or lumbosacral plexus following 3,320 operations on the abdominal aorta (0.3%). The incidence of this complication was 0.1% (2 of 1,901) after elective and 1.4% (3 of 210) after emergency abdominal aortic aneurysm repair, and 0.3% (4 of 1,209) after repair for occlusive disease. Three of the latter had prior clinical evidence of distal embolization. Eight grafts were bifurcated (aorto-iliac:four, aorto-femoral: three, aorto-ilio-femoral:one). One patient underwent extra-anatomic revascularization. Only two patients had supraceliac aortic cross-clamping and one patient underwent exclusion of both internal iliac arteries. Four patients had hypotension. Early mortality was 22% (two of nine). Severe perioperative complications, mostly due to associated visceral and somatic ischemia and sepsis, were present in seven of the nine patients. The extent and type of the neurologic injury correlated with long-term outcome. Patients with ischemic injury of the lumbosacral roots or plexus had better recovery. Attention to the pelvic circulation and the collateral blood supply is important. Use of gentle technique to prevent embolization, avoidance of hypotension and prolonged supraceliac cross-clamping, revascularization of at least one internal iliac artery, and the use of heparin may decrease but not eliminate paraplegia. Once this unexpected complication occurs, careful neurologic evaluation should be done to localize the lesion and aid prognosis.

Stump pressure, the contralateral carotid artery, and electroencephalographic changes.

Electroencephalographic (EEG) monitoring and measurement of stump pressure are the most widely employed methods of assessing the risk of cerebral ischemia during carotid endarterectomy. The status of the contralateral carotid artery has also been thought to influence the need for placing a shunt. The relationship of EEG monitoring, stump pressure, and the contralateral carotid artery has not been completely delineated. We retrospectively reviewed these three variables in 113 patients undergoing 124 carotid endarterectomies. The contralateral artery was classified as occluded, stenotic (greater than 50% decrease in diameter), or nonstenotic. There was a 48% incidence of EEG changes with contralateral occlusion, 18% with stenosis, and 21% with nonstenotic arteries (p = 0.014). There was a 73% incidence of EEG changes when the stump pressure was less than 25 mm Hg, 32% when the stump pressure was 25 to 50 mm Hg, and 2% when the stump pressure was greater than 50 mm Hg (p less than 0.001). There was no significant difference in the mean stump pressure for patients with occlusion (43.8 mm Hg), stenosis (44.7 mm Hg), or nonstenotic contralateral arteries (51.3 mm Hg). All patients with contralateral occlusion and a stump pressure less than 25 mm Hg had EEG changes. No patient with a stump pressure greater than 50 mm Hg and a patent contralateral artery had EEG changes. Although the incidence of EEG changes in the majority of patients was not accurately predicted by the stump pressure and the status of the contralateral carotid artery, stump pressure less than or equal to 50 mm Hg was sensitive, identifying 97% of patients with EEG changes.

Brachiocephalic aneurysm: the case for early recognition and repair.

Over a 40 year period (1950-1990) only 73 patients were treated surgically for brachiocephalic aneurysms. An operation was performed for 38 subclavian, 25 extracranial carotid, six innominate, three aberrant right subclavian, and one vertebral artery aneurysm. Twenty-three other associated aneurysms occurred in 14 patients. Five patients had an additional untreated brachiocephalic aneurysm, and nine patients had 18 aneurysms located in different anatomic regions. There were 40 men and 33 women with a mean age of 50.5 years (range 16 to 82 years). Forty patients (54.8%) presented with potentially life- or limb-threatening signs or symptoms, including stroke or transient ischemic attacks (31.5%), upper extremity ischemia (19.2%), and rupture (4.1%). Atherosclerosis was most common in innominate aneurysms (66.7%) but also occurred in subclavian (34.1%) and carotid aneurysms (12.0%). Thoracic outlet compression was a common etiology for subclavian aneurysms while trauma or spontaneous dissection was more frequent for carotid aneurysms. Six deaths (8.2%) occurred within 30 days of operation: two from rupture, three in association with concomitant cardiovascular operations, and one from emergency carotid ligation. There were no deaths with elective isolated surgical repair. Overall five and 10 year survival in patients with brachiocephalic aneurysms was 80.8% and 61.4%, respectively. The majority of brachiocephalic aneurysms present with life- or limb-threatening complications and are associated with a high mortality for emergency or concomitant repair. Early elective isolated surgical repair remains the optimal therapy.

Microvascular pedal bypass for salvage of the severely ischemic limb.

Bypass to the pedal arteries was performed with use of the operating microscope and standard microsurgical technique in 37 patients with severe, chronic ischemia of a lower extremity. Twenty-one patients (57%) had three or more cardiovascular risk factors, and 22 (59%) had diabetes. Preoperative arteriography identified a pedal artery suitable for bypass in all but one patient. The greater or lesser saphenous vein was used in all patients, most frequently as a nonreversed, translocated vein graft. An arm vein was used as part of a composite graft in only one patient. No early deaths occurred, and only one patient had a perioperative myocardial infarction. Although five grafts occluded within 30 days, four were successfully revised, and 36 patients had a patent graft at the time of dismissal from the hospital. At 1 year, the primary graft patency rate (patency without revision) was 60.8%, and the secondary patency rate was 68.8%. One early and six late amputations were performed; the cumulative 1-year limb salvage rate was 82.4%. Grafts with an intraoperative flow rate of 50 ml/min or more had a better patency rate than those with a lower flow rate. The presence of diabetes did not adversely affect long-term patency. Of the 34 patients who were alive at the time of this report, 27 (79%) had a functional foot that allowed ambulation, had no rest pain, and had no substantial loss of tissue. Pedal bypass should be considered for critical, chronic ischemia, even if the patient has an increased surgical risk and advanced distal atherosclerotic disease.